Semiconductor transistors may be subject to damage or altered behavior due to electrostatic discharge (ESD). ESD causes damage when charge builds up on a body (e.g., human body, machine, packaging container, etc.) which then comes in contact with the semiconductor transistor. If the charge that is built up on the body discharges into the semiconductor transistor, it can lead to a large and sudden burst of current flowing into the device. This current may undergo filamentation, which can melt the metal, contacts, and the semiconductor material as the power dissipates in the form of thermal energy. The melted location can cause the device to fail.
There are a variety of models/standards that are used for designing and testing against transistor failure due to electrostatic discharge. These include the human body model (HBM), the charge device model (CDM) and the machine model (MM). The HBM simulates ESD due to discharge from a human being. The CDM simulates a charged device's discharge when it contacts a conductor. The MM simulates discharge from a non-human source to the device, such as from production equipment or a tool. These models/standards provide a metric for designating the voltage that the device is likely to withstand without damage.
Semiconductor transistors may include shielding or other dissipative components to prevent the ESD from causing damage. These techniques, however, often require additional steps in the fabrication process or an adjustment to the design of the semiconductor transistor that complicate the design and fabrication process.